Semiconductor packages having various structures are used, each of which contains an electronic component such as an integrated circuit (IC) chip. Among these semiconductor packages, the one having a lead frame is widely used (e.g., a Quad Flat No Lead (QFN) package). The lead frame is made of thin plate metal which is used for fixing the IC chip and also used as an internal wire of the semiconductor package.
In the semiconductor package, such as the QFN package, the IC chip is bonded to a die pad of the lead frame with silver paste, solder, or the like. A terminal of the lead frame and the IC chip are electrically connected via a gold wire or an aluminum wire. After that, the IC chip and the wire are sealed by epoxy resin or the like in order to protect against humidity, dust, and external stress. The semiconductor package is manufactured through the above-described process. Those semiconductor packages may bring an advantage of being inexpensive and being excellent at the radiation of heat which is occurring in the IC chip.
Meanwhile, as for an electronic device, it is required to suppress unnecessary electromagnetic interference between electronic components in order to prevent malfunction. In the above-described semiconductor package, part of signals input or output to/from the IC chip may be radiated from the terminal and the wires as electromagnetic waves. Although the IC chip is covered with epoxy resin or the like, it is not covered with a conductive member such as metal. Therefore, electromagnetic waves are radiated outside from the semiconductor package. When the radiated electromagnetic waves cause interference between a plurality of semiconductor packages, the malfunction of the electronic device may occur.
As a semiconductor package which is capable of shielding electromagnetic waves occurring in the package, there is a structure disclosed in Patent Literature 1, for example. This is a semiconductor package, in which an IC chip is covered by a ceramic or metal cap having surfaces covered with conductive material, and the cap is attached to a radiator plate via a fin and a screw being attached to the side of the cap. In the semiconductor package, the cap, the fin, the screw, and the radiator plate are formed of conductive members, such as metal, and are electrically connected. Therefore, electromagnetic waves can be shielded.
In addition, as disclosed in Patent Literature 2, there is a structure, in which an IC chip is mounted on a printed circuit board in place of the lead frame, and wire bonding and resin molding are performed, and, after that, the surface of the molded resin is coated with an electromagnetic wave shielding coating.
Patent Literature 1: JP 2003-31987 A
Patent Literature 2: JP 2009-290217 A